In academic papers, the ranking of authors usually reflects their contribution and responsibility in the research process. The first author is usually the person who contributes the most to the paper. They are responsible for most of the research work, including experimental design, data collection and analysis. They are the main authors of the paper and are ultimately responsible for the content and quality of the paper.

The second author is the person who made the second contribution to the paper. They may have participated in some research work, such as data analysis or experimental design. They usually help the first author to write a paper and have a certain understanding and contribution to the content of the paper.

The correspondent is usually the leader of the research team or the person in charge of the project, and is responsible for the whole research project, including the planning, implementation and interpretation of the results. They usually participate in the writing of papers and are ultimately responsible for the content and quality of the papers. In addition, the correspondent is also responsible for communicating with journal editors and other researchers, and handling the publication of papers.

Generally speaking, the difference between the first author, the second author and the correspondent lies in their contribution and responsibility in the research process. The first author is the main author and the person in charge of the paper, the second author is the person who assists the first author to finish the paper, and the correspondent is the leader of the research group and the person in charge of the project. These different roles help to ensure the smooth progress of research and the quality of papers.